Telephone apparatus for the deaf



July 7, 1925. 1,544,647

M. J. JOHNSON I TELEPHONE APPARATUS FOR THE DEAF Filed April 1924 ATTORNEY -Patented July 7, 1925.

UNITED STATES PATENT OFFICE.

MANFRED J. JOHNSON, OF NAUGATUCK, CONNECTICUT, ASSIGNOR TO THE BRISTOL COMPANY, OF WATER-BURY, CONNECTICUT, A CORPORATION OF'CONNECTICUT.

TELEPHONE APPARATUS FOR THE DEAF.

Application filed April 29, 1924. 'Se'rial No. 709,792.

To all whom it may concern:

Be it known that I, MANFRED J. JOHNSON, a citizen of the United States, and a resident of Naugatuck, in the county of New Haven and State of Connecticut, have invented certain newand useful Improvements in Tele phone Apparatus for theDeaf, of which the following is a specification.

The invention relates to apparatus to assist the deaf in hearing.

Apparatus of this character consists generally of a sound collecting and transmitting member, a receiver. and a suitable battery associated therewith for supplying the necessary power for operating same. In some instances, vacuum tube relay means are included to amplify the transmitted sound. It will be understood that it is highly-desirable that such apparatus be made as light and compactas ssible, as it is usually to be carried aroun with the user; and especially where the apparatus comprises a differential type of transmitter. The present invention has for its object to provide apparatus of this character which shall give the requisite volume and quality of sound and size and weight. 4

To this end, the invention consists in dispensing'entirely with .the induction coil generally employed with a differential transmitter and connecting, in manner hereinafter set forth, the ordinary type of receiver with a differential type of microphone transmitter. Due to the novel arrangement of the'connections between the saidparticular type of transmitting mechanism and the receiver and the associated battery. it is possible' to appreciably increase the volume emitted by said receiver over that, ofthe usual unamplified type and at the same time more faithfully to reproduce vocal and musical sounds; also, to provide an electrically more efficient apparatus, obviating distortion, and affording, furthermore, a compact device of reduced weight thru theelimination of the usual comparatively heavy and cumbersome induction coil or transformer.

The nature of the invention, however, will best be understood when described in con nection with the accompanying drawings, in which I Fig. 1 illustrates the novel combination of transmitting microphone and receiver (with caps removed) with associated battery.

Fig. 2 is a diagrammatic view illustrating the electrical connections.

Referring to the drawings, 10 designates a microphone transmitter of the differential type comprising usually a movable electrode 11 located between a pair of stationary or rigid electrodes 12 and 13, suitable resistance'material such as granular carbon being interposed and the movable electrode 11. being connected suitably to a diaphragm 14 of the transmitter, all of which is well understood and forms no particular part of the present invention. The receiver 15 is,

generally speaking, of the usual type embodying a bi-polar permanent magnet having the pole pieces 16 and 17 about which are located respective solenoids '18 and 19 Wound in the usual manner; and there is located in electrode or neutral point 11 of the transmitter. It is desirable, also, to interpose a switch 23 for automatically maintaining the battery circuit open in order to conserve the energy of the battery when the audiphone is not in operation.

In the use of a differential transmitter, it will be understood that a double or branched circuit results, the resistance at any given moment in one branch being increased while the same is simultaneously decreased in the other branch. When the transmitter diaphragm is quiescent, the normal current flow is in opposite directions thru the respective solenoids 18 and 19 included in the branch circuits; and the magnetic flux of the receiver 15 is unafl'ected, as the current and resulting flux conditions are equal and opposite. When; however, the microphone transmitter diaphragm 14 is agitated and varies the resistances included between the movable'electrode 11 and the stationary; or rigid electrodes 12 and13 of the transmitter, the change due to these'oscillations causes. the current to rise in one of the branch circuits and simultaneously to diminish in the other; and as these effects are opposite, the resultant action produces a strong augmentation or reduction in the flux of the magnetic receiver 15. On a reverse oscillation, the current first falls to zero and'then reverses, producing a corresponding effect in the flux of the magnetic receiver. These fluctuations of flux are reproduced as vibrations of the diaphragm 20, and it will be appreciated that the variation is upon both sides of a zero line and not as pulsations of a normally flowing current, as in the usual type of audiphone.

By the expedient hereinbefore set forth, namely, tapping the connection between the solenoids of the receiver and connecting same directly to the neutral element of the differential transmitter, all of the advantages of such differential transmitter are retained and the electrical efiiciency of the combination is enhanced thru elimination of copper losses and elin'iination of magnetic leakage between windings of the transformer heretofore generally employed with such difl'erential microphone. Moreover, thru the elimination of an iron core of a transformer, distortion is reduced to a minimum; and as noted hereinbefore, the combination provides for a lesser number of parts, is reduced in weight and insures a more compact apparatus and thus greatly enhances its value when it is considered that the same is of necessity intended for carrying about, to alarge extent, by the user.

I claim 1. In a telephonic audiphone: a sound collgcting differential microphone transmitter; a receiver including a bi-polar permanent magnet, and a pair of solenoids about the poles thereof; an electric battery associated therewith; connections to place the microphone in series with the said solenoids; a connection from the neutral point of the differential microphone to one of the poles of said battery; and a connection from between the said solenoids of the receiver to the other pole of the battery.

2. In a telephonic audiphone: a sound colpoles thereof; an electric battery associated therewith; connections to place the microphone in series with the said solenoids; a connection from the neutral point of the differential microphone to one of the poles of said battery; a connection from between the said solenoids of the receiver to the other pole of the battery; and a switch included in the battery circuit.

3. In a telephonic audiphone: a transmit tcr comprising two stationary electrodes, a

movable electrode, and a diaphragm to move said movable electrode; a receiver comprising a bipolar permanent magnet, a pair of solenoids respectively mounted about the poles thereof andeach having two terminals, and a terminal of one solenoid beingconnected with the terminal. of the other. and a diaphragm under the influence of said poles; an electric battery; a connection from each of said stationary electrodes to the respective other terminals of the said solenoids; a connection from one pole of an electric battery; a connection from each of said stationary electrodes to the respective other terminals of the said solenoids; a

connection from one poleof said battery to the movable electrode of the transmitter; a connection from the other pole of saidbats. tery to the connection between the two said solenoid terminals; and a switch in'the battery circuit to normally prevent flow of electricity thru the microphone and receiver. Signed at VVaterbui-y, in the county of New Haven and State of Connecticut, this] 24th day of April A. D. 1924.

MANFRED J. JOHNSON. 

